1. Field of the Invention
The present invention generally relates to a wind turbine generator and a cable supporting structure for use therein, and more particularly to a cable supporting structure suitably used for holding a cable suspended from a nacelle of the wind turbine generator.
2. Description of the Related Art
A distinctive feature of the structure of the wind turbine generator is that major components constituting the wind turbine generator, such as a generator, a pitch control system and a yaw control system, are provided away from the ground. Specifically, a nacelle is provided on the top of a tower so that the nacelle is rotatable in the azimuth direction, and a generator, a gear box, a pitch control system and a yaw control system are installed in the nacelle.
Cables are suspended through the tower to connect the instruments installed in the nacelle with facilities provided on the ground (e.g., in-site power lines, a SCADA (Supervisory Control and Data Acquisition) and so on). The suspended cables include a power cable connected to the generator, and a control cable used to control the instruments installed in the nacelle. These cables are required to be securely fixed to stand vibrations caused by operations of the wind turbine generator.
One most typical method for fixing a cable to be suspended is to clamp the cable between a first plate which is fixed to the tower and a second plate which is opposed to the first plate, and to fasten the first and second plates with a bolt. U.S. Pat. No. 6,713,891 discloses such a structure.
One difficulty in fixing a cable is that the weight of the cable tends to be increased in a large-scaled wind turbine generator as developed recently. In a recent wind turbine generator, it is necessary to increase the diameter of the cable as the power output is increased, since a large current is required to flow through the cable. In addition, the height of the tower also tends to be increased in the recent wind turbine generator. Due to these two factors, the weight of the cable tends to be increased. In order, to address the increase in the weight of the cable, there also arises a requirement of increasing the fixing force of the cable. However, according to a study by the inventors, the cable may be insufficiently supported by a structure in which the cable is fastened with plates and a bolt.